Up to now, as a guide member for supporting an advancing/retreating movement of a movable member, such as a drawer in a piece of furniture or a system kitchen, there is known a slide rail unit equipped with an outer rail and an inner rail (see JP 11-201158 A, etc.). More specifically, the conventional slide rail unit is composed of an outer rail formed into a channel-like shape by bending and raising a pair of ball rolling portions along the longitudinal direction thereof, an inner rail one size smaller than the outer rail and also formed into a channel-like shape by bending and raising a pair of ball rolling portions, a large number of balls rolling on an inner side of the ball rolling portions of the outer rail and on an outer side of the ball rolling portions of the inner rail, and a retainer for aligning the balls at predetermined intervals between the outer rail and the inner rail. When the slide rail unit is used, the outer rail is fixed, for example, to the furniture main body, and the inner rail is fixed to either side surface of the drawer.
The inner rail is fit-engaged with the inner side of the outer rail through the intermediation of the balls, so the inner rail can be freely drawn out of the outer rail. As the inner rail is drawn out, the balls move within the outer rail together with the retainer, whereby it is possible for the drawer to be freely drawn into and out of the furniture main body.
As an example of the slide rail unit, there has also been proposed a type of slide rail unit in which, in order to avoid a half-open state of the drawer once closed and to eliminate inconvenience of the drawer opening of its own accord due to an earthquake, etc., when the inner rail has been accommodated in the outer rail to a certain degree, there is exerted on the inner rail an urging force drawing it into the outer rail, and by this urging force, the inner rail is drawn into the outer rail, and is retained as it is (JP 6-245830 A, JP 11-206489 A, JP 2004-344188 A).
In the slide rail unit disclosed in JP 6-245830 A, a roller provided on the inner rail side rolls on the outer rail, whereby the inner rail can freely advance and retreat along the outer rail; when drawing the inner rail into the outer rail, the roller climbs over a plate spring provided on the outer rail side, with the roller being urged by the plate spring in the direction in which the inner rail is drawn in. Further, unless the roller climbs over the plate spring in the opposite direction, the inner rail cannot be drawn out of the outer rail; thus, a slight locking force is exerted in the direction in which the inner rail is drawn out of the outer rail.
In the slide rail unit disclosed in JP 11-206489 A, a regulating member constructed of a plate spring is arranged in the outer rail so as to be free to rotate and in a state of being urged into a predetermined posture, and an engagement shaft to be engaged with the regulating member is provided fixedly and upright on the inner rail. When the inner rail is forced into the outer rail, the engagement shaft pressurizes the regulating member, which at first exerts an urging force in a direction of pushing back the inner rail; when, however, the inner rail is forced in against this urging force, the regulating member rotates to get over the dead center, and exerts this time an urging force to draw the inner rail into the outer rail. Further, when drawing the inner rail out of the outer rail, the regulating member is required to rotate to get over the dead center again. As a result, a slight locking force is exerted in a direction in which the inner rail is drawn out of the outer rail.
In the slide rail unit disclosed in JP 2004-344188 A, a guide case for a piece component urged by a spring is mounted to the outer rail; a pin provided upright on the inner rail side is engaged with or detached from the piece component sliding within this case, whereby the inner rail is drawn into the outer rail, and the inner rail drawn in is retained in the outer rail. The piece component, which is engaged with or detached from a pin on the inner rail side, is formed of synthetic resin in a predetermined shape, and is endowed with elasticity; thus, it undergoes elastic deformation within the case, thereby allowing engagement and detachment of the pin.    Patent Document 1: JP 11-201158 A    Patent Document 2: JP 6-245830 A    Patent Document 3: JP 11-206489 A    Patent Document 4: JP 2004-344188 A